Power clamps can be used to clamp components or workpieces which are to be secured together in the manufacture of products. For instance, power clamps are used to hold pieces together for a welding operation in the manufacture of automobiles.
Power clamps can be controlled by the application of a pressurized fluid, such as air, other gases, or a hydraulic fluid. The power clamp, also known as a clamp cylinder apparatus, can include a piston rod coupled to a piston which moves linearly in a reciprocal fashion within a housing. The movement of the piston in one direction causes an arm to rotate to a location to provide a clamping force. Movement of the piston in the opposite direction provides for removal of the arm from the article being clamped. The combination of the piston and the piston rod can have its linear motion stopped during unclamping at the end of its travel with a damper member. One example of such a clamp apparatus including a damper member is described in U.S. Patent Application Publication No. U.S. 2004/0041324 having a filing date of Aug. 19, 2003 the entirety of which is incorporated herein by reference.
Other known clamps include mechanisms for slowing down or stopping the piston. These mechanisms include those having a pneumatic cushion with built-in adjustable air cushion valves which can be adjusted based on the operating load and the operating speed. The air cushion operates only at the ends of the clamp cylinder stroke. Flow controls are also known which limit the speed of a clamp cylinder to acceptable limits to thereby reduce any impact loads which may occur on the clamp itself. Such a scheme, however, limits the clamp cylinder speed throughout the entire travel of the clamp cylinder.
The previously incorporated by reference U.S. Patent Application Publication No. 2004/0041324 describes an elastomeric bumper. The kinetic energy of the piston and piston rod combination is absorbed by the elastomeric bumper only at the very end of the clamp cylinder travel. The elastomeric bumper provides some shock absorption due to its material composition. There is, however, only slight movement of the bumper along the linear direction of the piston/piston rod due to compression of an elastomeric bumper.
Other known clamps include fixed orifices which have a built-in flow restriction to limit the clamp cylinder speed to an acceptable limit thereby reducing the impact loads on the clamp mechanism. As previously described for the flow controls, this scheme also limits the speed of the piston and piston rod throughout the entire travel of the clamp cylinder.